A. Field Of The Invention
The present invention relates generally to an improved wiper device and system for removing fluid including drilling mud, oil, water or the like, from the exterior surface of tubular articles including drill strings, work strings, sucker rods, or the like.
B. Description Of The Prior Art
In rotary drilling, a typical drill string will include a drill bit, drill collars, drill pipe and kelly joint. To rotate the drill string the kelly joint is placed through a kelly drive bushing which dropped into a rotary table. The rotary table is driven by a power unit. As the rotary table is turned, the drill string is rotated to allow the drill bit to cut the earth and rock, producing a well bore. At the same time drilling fluid (commonly referred to as drilling mud) is pumped down through the drill string and bit. The drilling mud cools and lubricates the bit and then flows upward through the annulus between the well bore and the drill string depositing the bit cuttings on the surface.
During rotary drilling, it is often necessary to remove the drill string from the well, otherwise known as "tripping". As the drill string is tripped from the well, the sections of drill pipe or tubulars are typically disconnected, in stands, from the remainder of the drill string and racked near the rotary table for convenient access. When the drill string is being tripped in this fashion, various fluids such as drilling mud, oil, water or the like cling to the outer walls of the stands and, if not removed, interfere with the handling of the stands or else drop onto the rig floor making it slippery and dangerous for the workers to operate around.
In the past, it has been been the practice to remove such fluids from the outer walls of the well string at the wellhead during tripping. This has been accomplished either by spraying water onto the drill string as it reaches the surface of the rig floor, or else by passing the drill string through a flexible or elastic wiper device. The water spraying method is undesirable since the water and fluids accumulate in the working area, and because the water dilutes the fluid which is often valuable and desirable to conserve.
The wiping devices previously used usually consisted of a rubber collar which is threaded over the upper end of the well string and held stationary by the rotary bushing in the rig's floor. The tight fit of such a stationary rubber collar does not permit the passage of larger diameter tools, such as stabilizers, reamers or drill bits, thus requiring removal of the collar before the trip can be completed. Further, the well string often sways back and forth during tripping which results in uneven pressure being applied to the external surfaces of the well string, thereby preventing even and consistent wiping thereof and causing excessive wear to the stationary rubber collar.
The wiper devices presently used incorporate a plurality of separate wiper pads that are held in place against the surface of the well string during tripping or insertion thereof, which pads can be retracted to allow passage of larger diameter tools without necessitating the removal of the wiper device. Although preferable to the stationary rubber collar devices, these devices are often impeded in operation by the buildup and accumulation of drilling mud, or other fluids, therein. Some of these devices are actuated with pneumatic cylinders which have their bodies and flexible supply lines exposed to the stripped fluids and to wear and damage caused during movement of their entire assemblies within their assembly containers. Further, these devices are solely operator actuated, and do not safeguard against the damage caused thereto when an operator fails to retract the wiper pads prior to rotation of the well string during operations. Examples of wiper devices are disclosed in Brown U.S. Pat. No. 3,733,641, Stevens U.S. Pat. No. 2,809,012, Baebel U.S. Pat. No. 2,718,021, and Head U.S. Pat. No. 2,026,036.
It is therefore an object of the present invention to provide a wiper device that overcomes the shortcomings of the prior art. More particularly, it is an object of the present invention to provide an improved wiper device that can be easily installed, repaired or removed without interfering with the drilling, completion of workover operations.
It is another object of the present invention to provide a wiper device which is simple and economical to build and maintain and which does not become easily jammed by the accumulation and caking of stripped fluids therein.
It is another object of the present invention to provide a wiper device which is equipped with water jets for periodic interior wash down to eliminate caking or stripped fluids therein without making a mess on the rig floor.
It is another object of the present invention to provide a wiper apparatus having encased wiper pads which will remain in place over the well bore throughout the drilling, completion or workover of oil and gas wells.
It is another objection of the present invention to provide a wiper apparatus that the wiper pads can be actuated by means of a pneumatic valve on a control panel mounted near the driller's console.
It is another objection of the present invention to provide a wiper apparatus that when the wiper pads are in their full extended position they will close off the well bore preventing foreign objects from falling and/or dropped into the well bore.
It is another object of the present invention to provide a wiper apparatus with a carriage guide that will allow the wiper pads to remain snugly around the drill string and follow the eccentric or lateral movement of the drill string.
It is another object of the present invention to prvide a wiper device which automatically retracts the wiper pads from engagement with the well string when the well string is rotating in operation.
It is another objection of the present invention to provide a wiper apparatus which will allow the passage of larger diameter tools that may make up the drill string and still wipe them dry.
It is another objection of the present invention to provide a wiper apparatus which is virtually maintenance free and equipped with water jets for periodic interior washdown to eliminate caking of drilling mud.
It is yet another object of the present invention to provide a wiper apparatus which will trap the mud as it is wiped from the external surface of the drilling string and direct it back into the well bore.